The present invention relates a PBGA (plastic ball grid array) type semiconductor device, more particularly a semiconductor die mounted circuit substrate thereof which mounts a lead pattern on one surface thereof and such a lead pattern comprises a ground plane which has a heat diffusion function as well as a grounding function and a plurality of spaced-apart outer connecting terminal lands to which solder balls are connected.
Recently, to meet the demand for miniaturing of semiconductor dies, down-sizing of the semiconductor devices and lowering of the production cost of the semiconductor devices, semiconductor devices called BGA which use a plurality of solder balls distributed in a grid array as the outer connecting terminals of semiconductor devices have been proposed, wherein such semiconductor devices are mounted on a mounting pad on the mounting plate. Such devices are, for example, disclosed in U.S. Pat. No. 5,045,921 (Lin et al.) and U.S. Pat. No. 5,216,278 (Lin et al).
Such a BGA type semiconductor device substantially comprises;
a semiconductor die mounting substrate wherein the substrate is prepared from polyimide resin tape or glass fabrics reinforced epoxy resin, a first lead pattern which is made of a plurality of spaced-apart first conductive leads is mounted on a peripheral portion of one surface of the substrate which encircles a die mounting region defined at the central portion of one surface of the substrate, and a second lead pattern which is made of a plurality of second conductive leads which are respectively connected with the first conductive leads by way of vias is mounted on the other surface of the substrate,
a semiconductor die mounted on the semiconductor die mounting region of the semiconductor die mounting substrate,
a plurality of bonding wires which provide an electrically conductive circuit by connecting a plurality of electrode pads mounted on the semiconductor die with a plurality of wire bonding pads of a plurality of first conductive leads,
a sealing resin agent which may preferably be made of epoxy resin and the like for sealing the mounting surface of the semiconductor die together with the bonding wires provided on the mounting surface, and
a plurality of solder balls which are respectively electrically connected with a plurality of outer connecting terminal lands of a plurality of the second conductive leads, solder balls being provided for connecting the semiconductor device to a printed wiring board located outside.
In the above construction, each first conductive lead is provided with a wire bonding pad at one end thereof and a via on the other end thereof which passes through the semiconductor die mounting board. The solder balls are mounted on the other surface of the semiconductor die mounting substrate in a grid array.
In the conventional BGA type semiconductor device (PBGA type semiconductor device in a more accurate term) having the above-mentioned construction, however, since a multiplicity of bonding wires which are connected with the semiconductor die mounted on one surface of the substrate, a multiplicity of conductive leads which constitute the first lead pattern and a multiplicity of conductive leads which constitute the second lead pattern and are connected with the conductive leads of the first lead pattern by way of vias are concentrated or compacted at one place, the device has following drawbacks.
a) Heat generated from the semiconductor die cannot be diffused sufficiently so that any semiconductor die which consumes an electric power exceeding, for example, 3 watt cannot be mounted.
b) Due to magnetic noises such as cross talks which are caused by crossing or coming close of adjacent signal lines as well as deterioration of electrical characteristics caused by elongated conductive circuits, high frequency characteristics is deteriorated so that the semiconductor device having a response of more than 100 MHz cannot be produced.
c) Furthermore, in the conventional semiconductor device, since the front surface of the electrically insulating substrate on which the first conductive leads are mounted is directly sealed by resin, a sufficient adhering strength is not achieved between the insulating substrate and the sealed resin. Accordingly, the sealed resin is easily peeled off giving rise to an infiltration of moisture through a gap defined between the insulating substrate and the sealed resin thus showing poor resistance to moisture.
Accordingly, it is an object of the present invention to provide a semiconductor device which can meet a demand for a highly improved function and performance by overcoming the above-mentioned drawbacks of conventional semiconductor device, wherein the conductive circuits can be made considerably short thus effectively restricting the occurrence of cross talk noises caused by the parasitic current on the conductive layer, improving the heat diffusion of the semiconductor device and effectively preventing malfunctions of semiconductor device caused by electromagnetic noises.